1. Field of the Invention
This invention relates to the actuation of valves in internal combustion engines, and more particularly to cam and pushrod assemblies for accomplishing opening and closing of the valves at desired angular positions of the crankshaft.
2. Description of the Prior Art
Most internal combustion engines operate the intake and exhaust valves from rotating camshafts having lobes formed to lift the valve heads from their seats, either directly through valve rods. In the case of valve-in-head engines, the valves are operated by means of lifter rods actuated by the cams and acting on the valves through rocker arms. Problems are encountered in driving separate camshafts in accurate synchronization with the rotation of the crankshaft, both gears and belts being used for this purpose. These systems are expensive to manufacture and synchronization is lost as the gears wear and/or the belts stretch.
The present invention proposes forming or mounting the valve operating cam directly on the engine crankshaft for rotation therewith. The only disclosure that might be characterized as prior art known to applicant is Blodgett U.S. Pat. No. 1,183,795, which utilizes cams formed on the crankshaft throws to operate the valves. In Blodgett the valve rods are not pushed directly by the eccentric cams. Instead, separate members, held and positioned by five fingers, are utilized; apparently to accomodate the system to a four stroke cycle engine. This is necessary because, in a four stroke engine, the crankshaft rotates twice for each opening of the valve.
The structure of the present invention completely eliminates the complicated mechanism of Blodgett. As utilized with two-stroke engines, the apparatus of the present invention is simple and sturdy, and avoids any problems of synchronizing the cam with the crankshaft, since they rotate together.